1. Field of the Invention
The present invention relates to a method for removing a patterned photoresist. In particular, the present invention relates to a method to use a non-oxidative pre-treatment prior to removing a patterned photoresist so that the patterned photoresist is substantially influenced and can more easily be removed.
2. Description of the Prior Art
During the manufacturing process of semiconductors, a lithographic technique is often used together to transfer a pre-determined pattern into a substrate or to carry out a selective treatment on the substrate. During such process, a photoresist material layer is usually first uniformly formed on the substrate. Later, an exposure technique and a development technique are used to pattern the photoresist material layer to define a pre-determined layout structure of the semiconductor elements.
Removing the photoresist is usually the last step of the patterning technique or the selective treatment. It requires that the photoresist be completely and thoroughly removed to ensure the cleanness of the following steps. In the conventional methods, an oxygen-containing ashing procedure is mostly used to carry out a dry photoresist strip (dry PR strip), which uses an oxygen plasma to react with the photoresist material which is basically composed of hydrocarbons to remove it. The problem of residue ash which is caused by the photoresist material reacting with the oxygen plasma should be avoided. Besides, the silicon material in the substrate is susceptible to be consumed in this method.
Accordingly, another current method which uses a sulfuric-peroxide mix liquid (SPM) of high temperature is proposed. The sulfuric acid and the peroxide form Caro's acid to completely oxidize the photoresist material which is basically composed of organic compounds. This is called a wet photoresist strip (wet PR strip). On one hand, the photoresist material can be removed, and on the other hand this method makes the film layers which are covered by the photoresist material layer or the silicon material in the substrate much less susceptible to be consumed.
However, some manufacturing processes of semiconductor elements may substantially change the properties of the patterned photoresist material layer so that the sulfuric-peroxide mix (SPM) of high temperature can no longer completely remove the photoresist material layer from the substrate as expected. In order to conveniently remove the photoresist material layer, a novel method for removing a photoresist is therefore needed.